Hinge through which an electrical circuit is completed with means to interrupt the circuit

ABSTRACT

A hinge has leaves provided with aligned knuckles through which a hinge pin extends. The pin is anchored to the knuckle of one of the leaves and carries a dielectric contact spindle on which slip rings are mounted. The knuckle of the other leaf has a dielectric receptacle provided with contact blades which engage the slip rings. The engaged contact blades and slip rings complete electrical circuits through the hinge, but do not interfere with disassembly of the hinge. One slip ring is split so that the circuit through it is interrupted when the hinge reaches a prescribed position. Wires extend from the slip rings and contact blades through the hinge knuckles and also through grooves milled into the end edges of the leaves, and are thereby completely concealed.

United States Patent Peterson Sept, 24, 1974 [75] Inventor: Francis C.Peterson, Affton, Md.

[73] Assignee: C. Hager & Sons Hinge Manufacturing Company, St. Louis,Mo.

[22] Filed: July 2, 1973 [21] Appl. No.: 375,788

[52] US. Cl. ZOO/61.7, 339/4 [51] Int. Cl. H0lh 3/16 [58] Field ofSearch ZOO/61.62, 61.82; 339/4, 339/6, 8

[56] References Cited UNITED STATES PATENTS 426,705 4/1890 BleakleyZOO/61.7 612,192 10/1898 Chandler 339/4 1,744,040 1/1930 Elzer 339/41,861,547 6/1932 Parkhurst.... ZOO/61.7

2,608,638 8/1952 Daiger 339/4 UX 2,778,000 1/1957 FOREIGN PATENTS ORAPPLICATIONS 1,132.63 11/1956 France 339/4 Primary ExaminerJames R.Scott Attorney, Agent, or Firm--Gravely, Lieder & Woodruff 57 ABSTRACT Ahinge has leaves provided with aligned knuckles through which a hingepin extends. The pin is anchored to the knuckle of one of the leaves andcarries a dielectric contact spindle on which slip rings are mounted.The knuckle of the other leaf has a dielectric receptacle provided withcontact blades which engage the slip rings. The engaged contact bladesand slip rings complete electrical circuits through the hinge, but donot interfere with disassembly of the hinge. One slip ring is split sothat the circuit through it is interrupted when the hinge reaches aprescribed position. Wires extend from the slip rings and contact bladesthrough the hinge knuckles and also through grooves milled into the endedgesof the leaves, and are thereby completely concealed.

IG CIa iins, IO DraWing Figures HINGE THROUGH WHICH AN ELECTRICALCIRCUIT IS COMPLETED WITH MEANS TO INTERRUPT THE CIRCUIT BACKGROUND OFTHE INVENTION This invention relates in general to hinges and, moreparticularly, to a hinge through which an electrical circuit iscompleted.

To provide better security for office and other types of commercialbuildings, the owners of such buildings are turning more and more toelectrically operated surveillance systems. These systems monitor doorsat critical locations in the buildings as well as the locks on suchdoors, and energize an alarm in a remote security office when a door isopened by an unauthorized person or when the lock for the door is notproperly set.

One way to maintain surveillance over a door and its lock is to hingethe door on a so-called contact hinge. A hinge of this nature isdisclosed in US. Pat. No. 3,659,063 and includes spring loadedcontactors in one leaf and a corresponding number of contacts in theother leaf. When the door is closed the contactors engage the contacts,thus enabling electrical circuits to be completed through the hinge. Inmore sophisticated arranger'nents, several circuits are completedthrough the hinge, and most of them are extended to the lock forcontrolling it or maintaining surveillance over it. However, one of thecircuits usually maintains surveillance over the hinge itself, and thecircuit sounds an alarm when broken at the hinge, thus indicating thatthe door is open. In a contact hinge of the foregoing type, the contactsand contactors are exposed when the door is open or slightly ajar, andone knowing the circuitry could foil the security system by shorting outthe proper contacts or contactors.

A way to maintain surveillance over the door alone is to use a so-calledswitch hinge. A hinge of this type is disclosed in US. Pat. No.3,715,537 and one leaf of the hinge has a switch which is actuated whenthe hinge opens. Again the switch is exposed when the door is open orslightly ajar.

Hinges also exist having hollow pins through which wires extend. Thesehinges are of course suitable for maintaining surveillance over locks'in'the doors on" which they are installed, but they do not permit easyremoval of the door for repairs of refitting. Moreover, hinges of thisnature usually have holes drilled transversely through the leavesthereof to house wires without exposing those wires when the door isopen. These holes are extremely difficult to drill and result in manyrejected hinge leaves.

SUMMARY OF THE INVENTION One of the principal objects of the presentinvention is to provide a hinge for extending an electrical circuit intoa door without exposing any of the wires of the circuit either when thedoor is open or closed. Another object is to provide a hinge whichalters an electrical circuit as the door moves away from its fullyclosed position without exposing any of the electrical circuitry, eitherwhen the door is open or closed. A further object is to provide a hingeof the type stated which enables the door to be easily removed from itsdoor frame. An additional object is to provide a hinge of the typestated which is easily manufactured and does not result in a high partsrejection rate. These and other objects and advantages will becomeapparent hereinafter.

The present invention is embodied in a hinge having slip rings andcontact elements carried by different knuckles thereof so that anelectrical circuit can be completed through the hinge. One of the sliprings is split to break a circuit when the hinge reaches a prescribedposition. The leaves have grooves in which the wires of the circuit arecontained. The invention also consists in the parts and in thearrangements and combinations of parts hereinafter described andclaimed.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form partof the specification and wherein like numerals and letters refer to likeparts wherever they occur.

FIG. I is a perspective view of the hinge of the present invention setinto a hinge jam and door;

FIG. 2 is an exploded perspective view showing the hinge from its backside;

FIG. 3 is an elevational view, partially broken away and in section, ofthe frame leaf of the hinge;

FIGS. 4 and 5 are sectional views taken along lines 44 and 5-5,respectively, of FIG. 3;

FIG.v 6 is a top view of the frame leaf and hinge pin;

FIG. 7 is a elevational view, partially broken away and in section, ofthe door leaf of the hinge;

FIG. 8 is a sectional view taken along line 8-8 of FIG. 7;

FIG. 9 is a sectional view taken perpendicular to the hinge axis at thesplit slip ring when the contact blade for that ring is at the slit sothat the blade is electrically isolated from the ring; and

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9.

DETAILED DESCRIPTION Referring now to the drawings (FIG. 1 H designatesa full mortise hinge of the loose joint variety for supporting a door 2on the hinge jamb 4 of a door drame. The hinge H is used in conjunctionwith at least one other hinge and preferably two other hinges. Theseother hinges (not shown) are also full mortise hinges set into the door2 and hinge jamb 4 and may likewise be of the loose joint variety orthey may be of the more typical hinge construction with three or moreinterlocking knuckles. The hinge H differs from the other hinges in thatit possesses the capability of extending electrical circuit from thehinge jamb 4 into the door 2 for remotely operating a lock on the door 2or for maintaining surveillance over the lock or door 2 or both. Iffurther possesses the capability of breaking or otherwise changing anelectrical circuit as it is opened to signal when the door 2 is ajar oris opened.

The hinge H includes (FIGS. 1 and 2) a frame leaf l0 and a door leaf 12,both of which are preferably formed from steel or some other suitablemetal and are held together by a hinge pin 14 secured in the frame leaf10. Each leaf l0 and 12 has a plurality of countersunk holes 16 foraccommodating flat head screws used to secure the leaves 10 and 12 tothe frame 4 and door 2, respectively.

The frame leaf It) is mortised into the hinge jamb 4 with one of itsside edges generally aligned with the edge of that jamb, and along thelower half of that side edge the leaf 10 is rolled into an integrallyformed knuckle 20 having a bore 20 which is counterbored at its upperend. The hinge pin 14 is pressed into the bore 22 and projects upwardlyfrom the upper end of the knuckle 20 (FIG. 3), but does not extend allthe way through the knuckle 20. Fitted into the lower end of the bore 22is a plug 24 which closes the lower end of the knuckle 20.

Milled into the lower edge of the frame leaf is a downwardly openinggroove 26 (FIGS. 3-5) which extends from the bore 22 of the knuckle allthe way across the lower end of the leaf 10. The groove 26 receives ametal closure strip 28 which fits snugly therein, but can be easilypried out of the leaf 10 to expose the groove 26 when the leaf 10 isremoved from the hinge jamb 4. The mortising of the leaf 10 conceals theclosure strip 28 and prevents it from being removed when the leaf 10 issecured to the hinge jamb 4. One end of the closure strip 28 abuts theplug 24, while the other end is flush with the other side edge of theleaf 10. The closure strip 28 is not as deep as the groove 26 and as aresult a small cavity exists within the leaf 10 immediately above theclosure strip 28 (FIGS. 3 and 5). This cavity opens into the bore 22 ofthe knuckle 20 below the hinge pin 14. The cavity formed within thegroove 26 opens toward the hinge jamb 4 through a notch 30 which alignswith a hole extending through the hinge jamb 4.

The hinge pin 14 is formed from steel or some other suitable metal andintermediate its ends it is provided with a flange 32 which fits intothe upper counterbore in the bore 22 and locates the pin axially withinthe knuckle 20 (FIG. 3). The hinge pin 14 has a bore 34 extendingcompletely through it and at its upper end is tapered and provided witha cross slot 36 (FIG. 6).

Fitted into the cross slot 36 at the upper end of the hinge pin 14 is acontact spindle 38 (FIG. 3) which is formed from a dielectric materialsuch as Lexan. The dielectricspindle 38 is anchored firmly in the slot36 of the pin 14 and projects upwardly from the tapered end of the hingepin 14, remaining coaxial therewith. Embracing'the spindle 38 are aplurality of metallic slip rings 40, which are axially spaced andelectrically isolated from one another by the dielectric material of thespindle 38. The slip rings 40 are anchored firmly on the spindle 38 andextend 360 around it. In addition to the full slip rings 40, thedielectric spindle 38 also carries a split slip ring 42 which isanchored firmly on it. The ring 42 is much like the slip rings 40 and iselectrically isolated from these rings by the dielectric material of thespindle 38. However, the slip ring 42 does not ex tend a full 360 aroundthe spindle 38. On the contrary, it possesses an axially extending slit44 which is occupied by the dielectric material of the spindle 38 (FIGS.9 and 10). In this regard, the dielectric material extends out to theouter surfaces of the slip rings 40 and 42 so that the exposedcircumferential surfaces of the slip rings 40 and 42 and of the spindle38 are flush. In other words, the slip rings 40 and 42 are embedded inthe dielectric material of the spindle 38.

Each slip ring 40 and 42 on its inside face is connected to a separatewire 44 and these wires are embedded in the dielectric material of thespindle 38. The wires 44 leave the spindle 38 and pass through the bore34 of the hinge pin 14. At the lower end of the pin bore 34, the wires44 enter the bore 22 of the hinge knuckle and then pass into the groove26 extending along the bottom of the frame leaf 10. The wires 44 leavethe frame leaf 10 at the notch 30 in the back thereof and pass into thehinge jamb 4 (FIG. 1 beyond which they may be connected to an alarm orremote control switch for operating a lock on the door 2.

The door leaf 12 (FIG. 7) is practically identical to the frame leaf 10,only it turned upside down with respect to the frame leaf 10. The doorleaf 12 includes a knuckle 50 having a bore 52 extending through it, andthis bore is sized to receive the portion of the hinge pin 14 projectingupwardly from the knuckle 20 on the frame leaf 10. A clearance fitexists between the pin 14 and the bore 52 so that the leaf 12 will pivoteasily with respect to the leaf 10. The upper end of the bore 52 isfitted with a plug 54. Along the upper edge of the leaf 12 an upwardlyopening groove 56 is milled into the leaf l2 and this groove 56 opensinto the bore 52 of the knuckle 50. The groove 56 receives a closurestrip 58 which is not as deep as the groove 56, so that a portion of thegroove 56 exists below the strip 58. The strip 58 may be pried out ofthe groove 56, but only when the leaf 12 is removed from the door 2,since the mortising prevents such removal when the leaf 12 is attachedto the door 2. The groove 56 opens rearwardly through a notch 60 in thedoor leaf 12, and this notch registers with a hole in the door 2 (FIG.1).

The bore 52 of the knuckle 50 on the door leaf 12 contains a receptacle64 (FIGS. 7 and 8) which is formed from a dielectric material such asLexan." The receptacle 64 is fitted tightly in the bore 52 and has adownwardly opening socket 66 which loosely receives the contact spindle36 projecting from the hinge pin 14 on the knuckle 20 of the frame leafl0. Embedded into the dielectric material of the receptacle 64 are metalcontact blades 68, the spacing between which corresponds to the spacingbetween the slip rings 40 on the contact spindle 36. EAch contact blade68 is spring loaded to bear against one of the slip rings 40 when thehinge H is assembled, and the spring loading results from the naturalresiliency of the metal. Likewise, another contact blade 70 identical tothe blades 68 is embedded in the dielectric material, and this blade ispositioned to align with and contact the split slip ring 42. In thisregard, the axial position of the receptacle 64 in the bore 52 of theknuckle 50 is such that when that knuckle 50 is fitted over the hingepin 14 and brought against the knuckle 20, each of the contact blades 68in the receptacle 64 will bear against a different full slip ring 40,while contact blade 70 will bear against the split slip ring 42. As tothe circumferential position of the receptacle 64 with respect to theknuckle 50, it is such that the blade 70 bears against the split slipring 42 when the leaves 10 and 12 face each other, as would be the casewhen the door 2 is closed, but moves across the slit 44 immediately uponthe opening of the hinge 14 (FIG. 9), that is as the door 2 is opened.Moreover, the contact between the contact blade 70 and the split slipring 42 is one of line contact so that the blade 70 does not bridge theslit 44 as it moves across it. The contact blades 68 and 70 and thecontact spindle 38 are configured such that the receptacle 64 can befitted over and removed from the spindle 36 without bending or otherwisedamaging the contact blades 68 and 70. Thus, the leaves 10 and 12 of thehinge H are easily separated.

Each of the contact blades 68 and 70 is connected to a different thinwire 72 which passes through the dielectric material of the receptacle64 and into the bore 52 of the knuckle 50. The wires 72 also passthrough the groove 56 along the upper edge of the door leaf 12 and leavethe leaf 12 through the notch 60 in the back face thereof. Beyond thenotch 60, the wires 72 pass into the door (FIG. 1). Some of the wires 72may be connected to an electrically operated lock for the door 2.

INSTALLATION AND OPERATION The frame leaf is installed on the hinge jamb4 of the door frame with the hinge pin 14 projecting upwardly, while thedoor leaf 12 is installed on the side edge of the door 2 (FIG. 1). Bothinstallations are of the mortise variety. The wires 72 leading from theframe leaf 10 are connected to an alarm in a remote security room, whilethe wires 46 leading from the door leaf 72 are connected to the lock inthe door 2.

To install the door 2 in its frame, the door 2 is elevated slightly to aposition in which the knuckle 50 of the door leaf 12 is above the hingepin 14 on the frame leaf 10 (FIG. 2). With the bore 52 of the knuckle 50aligned with the hinge pin 14, the door 2 is lowered and the hinge pin14 enters the bore 52 of the knuckle 50. When the knuckle 50 comes torest on knuckle 20, the contact spindle 38 will be in its properposition within the socket 66 of the dielectric receptacle 64, and inthat position each contact blade 68 wi11 engage a differ ent full slipring 40, while the contact blade 70 will engage either the split slipring 42 or the slit 44 in that ring. The other hinges for the door areinstalled in the usual manner.

When the door 2 is completely closed, the contact blade 70 engages thesplit slip ring 42. However, when the door 2 opens the receptacle 64rotates with the knuckle 50, and this rotation causes the contact blade70 to move over the slit 44 between the ends of the ring 42 (FIG. 9).The circuitry is such that the break in the circuit through the blade 70and the slip ring 42 causes an alarm to be energized at a remote controlroom. The circuits through the other contact blades 68 and theircorresponding slip rings 40 remain complete irrespective of the positionof the hinge.

None of the wires 46 or 72 is exposed or easily accessible so that thealarm system is almost impossible to defeat. Nevertheless, the door 2can be removed from the hinge jamb 4 without cutting or separating anywires. Thus, maintenance work is not in any way impeded.

This invention is intended to cover all changes and modifications of theexample of the invention herein chosen for purposes of the disclosurewhich do not constitute departures from from the spirit and scope of theinvention.

What is claimed is:

l. A hinge comprising first and second leaves having aligned knuckles; ahinge pin fixed in the knuckle of the second leaf and projected beyondthat knuckle into the knuckle of the first leaf for holding the leavestogether while allowing them to pivot relative to each other; aninsulative spindle on the hinge pin and being located within the knuckleof the first leaf, the spindle being made from a dielectric material; aslip ring on the spindle and being fixed in position with respect to thesecond leaf, the slip ring having a slit therein which is occupied bythe dielectric material of the spindle; a contact element carried by theknuckle of the first leaf and generally fixed in position with respectto the first leaf, the contact element being positioned opposite theslip ring on the spindle such that it will contact either the slip ringor the dielectric material in the slit of the slip ring, depending onthe position of the leaves,

whereby at a prescribed position of the leaves the slip ring and contactelement will not be in electrical contact so that an electrical currentwill not be conducted through the hinge and in other positions thecontact element and slip ring will be in contact to conduct anelectrical current through the hinge.

2. A hinge according to claim 1 wherein the slip ring is arcuate and hasits center of curvature at the axis of the hinge pin.

3. A hinge according to claim 1 wherein the contact element is flexibleand carried by a receptacle fixed in position in the knuckle of thefirst hinge, the receptacle having a socket which receives the spindlemounted on the hinge pin.

4. A hinge according to claim 1 wherein a wire extends from the slipring axially through the knuckle on the second leaf.

5. A hinge according to claim 1 wherein each leaf has only one knucklewhich extends substantially to one end edge thereof.

6. A hinge according to claim 5 wherein wires lead from the contactelement and slip ring; and wherein the wire leading from the slip ringextends through the knuckle of the second leaf and the wire leading fromthe contact element extends through the knuckle of the first leaf.

7. A hinge according to claim 6 wherein each leaf has a goove along thatend edge thereof leading to its knuckle, and the wires further extendthrough grooves so they are not outwardly exposed.

8. A hinge comprising: first and second leaves having aligned knuckles;a .hinge pin extending through the knuckles for holding the leavestogether while allowing them to pivot relative to each other, each leafhaving a groove along an end edge thereof leading to the interior of theknuckle thereon; a contact element in one of the knuckles and fixed inposition with respect to the first leaf; a slip ring engaged by thecontact element and issulatively mounted fixed position with respect tothe second leaf; a wire extending from the contact element and throughthe knuckle and groove of the first leaf; and another wire extendingfrom the slip ring and through the knuckle and groove of the second leafthe wires when the hinge is open being completely obscured at thenormally exposed side of the hinge.

9. A hinge according to claim 8 wherein the grooves are formed in andopen out of the end edges of the first and second leaves.

10. A hinge according to claim 9 wherein each hinge has only oneknuckle.

lll. A hinge according to claim 10 wherein closure strips are fittedinto the grooves to close the grooves.

12. A hinge according to claim 10 wherein the leaves have apertureswhich open into the grooves and the wires leave the hinge through theapertures.

13. A hinge according to claim 12 wherein the leaves have front and backfaces with the front faces being presented opposite and in closeproximity to each other when the hinge is closed; and wherein theapertures open out of the back faces but not the front faces of theleaves.

14. A hinge comprising first and second leaves formed from metal andhaving knuckles aligned along a common axis and connected together sothat the leaves can pivot relative to each other about the common axisof the knuckles; a first insulative element formed from a dielectricmaterial and fixed in position with respect to the knuckle of the firstleaf; an arcuate slip ring mounted firmly on the first insulativeelement concentric to the common axis, the slip ring being electricallyconductive and having an axially extending slit therein which isoccupied by the dielectric material of the first insulative element; asecond insulative element formed from a dielectric material and fixed inposition with respect to the second leaf, an electrically conductivecontact element mounted on the second insulative element and positionedopposite the slip ring on the insulative material such that it willcontact either the slip ring or the dielectric material in the slit ofthe slip ring, depending on the position of the leaves, whereby at somepositions of the leaves the slip ring and contact element will be inelectrical contact and in other positions they will not so that when insaid other positions an electrical current will not be conducted throughthe hinge by way of the contact element and slip ring; the insulativeelements, the slip ring, and contact element all being wholly containedin and completely obscured by at least one of the hinge knuckles, andthe electrically conductive slip ring and contact element being whichprojects into the knuckle of the second leaf.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 838 r234 Dated September 24 1974 Inventor(s) Francls rson It is certifiedthat error appears in the aboveidentified patent and that said LettersPatent are hereby corrected as shown below:

Column-l, line 48 the second occurrence of the preposition "of" shouldbe "or";

Column" 6, claim a, line 44 "i ssulati vely" should be "insulatively",and "fixed" should be "in "fixed".

Signed and sealed this 3rd day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN, Arresting Officer Commissioner ofPatents FORM (10-69) 1 uscoMM-oc 60376-P69 .5. GOVERNMENT PRINTINGOFFICE [9.9 0"365'33.

UNITED STATES PATENT OFFICE 1 CERTIFICATE OF CORRECTION Patent NO. ,234Dated September 24, 1974 Inventor(s) Francls rson It is certified thaterror appears, in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 48 the second occurrence of the preposition "of" shouldbe "or" Column' 6, claim 8, line 44 "issulatively" should be"insulatively", and "fixed" should be "in "fixed" Signed and sealed this3rd day of December 1.974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN I Attesting Officer Commissioner ofPatents USCOMM-DC 60376-P69 u.s. sovsmmsu'r PRINTING OFFICE waso-ass-su.

FORM PC4050 (1069)

1. A hinge comprising first and second leaves having aligned knuckles; ahinge pin fixed in the knuckle of the second leaf and projected beyondthat knuckle into the knuckle of the first leaf for holding the leavestogether while allowing them to pivot relative to each other; aninsulative spindle on the hinge pin and being located within the knuckleof the first leaf, the spindle being made from a dielectric material; aslip ring on the spindle and being fixed in position with respect to thesecond leaf, the slip ring having a slit therein which is occupied bythe dielectric material of the spindle; a contact element carried by theknuckle of the first leaf and generally fixed in position with respectto the first leaf, the contact element being positioned opposite theslip ring on the spindle such that it will contact either the slip ringor the dielectric material in the slit of the slip ring, depending onthe position of the leaves, whereby at a prescribed position of theleaves the slip ring and contact element will not be in electricalcontact so that an electrical current will not be conducted through thehinge and in other positions the contact element and slip ring will bein contact to conduct an electrical current through the hinge.
 2. Ahinge according to claim 1 wherein the slip ring is arcuate and has itscenter of curvature at the axis of the hinge pin.
 3. A hinge accordingto claim 1 wherein the contact element is flexible and carried by areceptacle fixed in position in the knuckle of the first hinge, thereceptacle having a socket which receives the spindle mounted on thehinge pin.
 4. A hinge according to claim 1 wherein a wire extends fromthe slip ring axially through the knuckle on the second leaf.
 5. A hingeaccording to claim 1 wherein each leaf has only one knuckle whichextends substantially to one end edge thereof.
 6. A hinge according toclaim 5 wherein wires lead from the contact element and slip ring; andwherein the wire leading from the slip ring extends through the knuckleof the second leaf and the wire leading from the contact element extendsthrough the knuckle of the first leaf.
 7. A hinge according to claim 6wherein each leaf has a goove along that end edge thereof leading to itsknuckle, and thE wires further extend through grooves so they are notoutwardly exposed.
 8. A hinge comprising: first and second leaves havingaligned knuckles; a hinge pin extending through the knuckles for holdingthe leaves together while allowing them to pivot relative to each other,each leaf having a groove along an end edge thereof leading to theinterior of the knuckle thereon; a contact element in one of theknuckles and fixed in position with respect to the first leaf; a slipring engaged by the contact element and issulatively mounted fixedposition with respect to the second leaf; a wire extending from thecontact element and through the knuckle and groove of the first leaf;and another wire extending from the slip ring and through the knuckleand groove of the second leaf the wires when the hinge is open beingcompletely obscured at the normally exposed side of the hinge.
 9. Ahinge according to claim 8 wherein the grooves are formed in and openout of the end edges of the first and second leaves.
 10. A hingeaccording to claim 9 wherein each hinge has only one knuckle.
 11. Ahinge according to claim 10 wherein closure strips are fitted into thegrooves to close the grooves.
 12. A hinge according to claim 10 whereinthe leaves have apertures which open into the grooves and the wiresleave the hinge through the apertures.
 13. A hinge according to claim 12wherein the leaves have front and back faces with the front faces beingpresented opposite and in close proximity to each other when the hingeis closed; and wherein the apertures open out of the back faces but notthe front faces of the leaves.
 14. A hinge comprising first and secondleaves formed from metal and having knuckles aligned along a common axisand connected together so that the leaves can pivot relative to eachother about the common axis of the knuckles; a first insulative elementformed from a dielectric material and fixed in position with respect tothe knuckle of the first leaf; an arcuate slip ring mounted firmly onthe first insulative element concentric to the common axis, the slipring being electrically conductive and having an axially extending slittherein which is occupied by the dielectric material of the firstinsulative element; a second insulative element formed from a dielectricmaterial and fixed in position with respect to the second leaf, anelectrically conductive contact element mounted on the second insulativeelement and positioned opposite the slip ring on the insulative materialsuch that it will contact either the slip ring or the dielectricmaterial in the slit of the slip ring, depending on the position of theleaves, whereby at some positions of the leaves the slip ring andcontact element will be in electrical contact and in other positionsthey will not so that when in said other positions an electrical currentwill not be conducted through the hinge by way of the contact elementand slip ring; the insulative elements, the slip ring, and contactelement all being wholly contained in and completely obscured by atleast one of the hinge knuckles, and the electrically conductive slipring and contact element being electrically isolated from the metalhinge leaves by the insulative elements.
 15. A hinge according to claim14 wherein the second insulative element has a socket therein whichreceives the first insulative element.
 16. A hinge according to claim 14wherein the leaves are connected together by a hinge pin which ismounted firmly in the knuckle of the first leaf and projects into theknuckle of the second leaf; and wherein the first insulative element isa spindle which is mounted firmly on that portion of the hinge pin whichprojects into the knuckle of the second leaf.